In vivo assembly of bacterial partition condensates on circular supercoiled and linear DNA
2024
Sekkouri Alaoui, Hicham | Quèbre, Valentin | Delimi, Linda | Rech, Jérôme | Debaugny-Diaz, Roxanne | Labourdette, Delphine | Campos, Manuel | Cornet, François | Walter, Jean-Charles | Bouet, Jean-Yves | Laboratoire de microbiologie et génétique moléculaires - UMR5100 (LMGM) ; Centre de Biologie Intégrative (CBI) ; Université Toulouse III - Paul Sabatier (UT3) ; Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3) ; Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS) | Laboratoire Charles Coulomb (L2C) ; Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM) | Toulouse Biotechnology Institute (TBI) ; Institut National des Sciences Appliquées - Toulouse (INSA Toulouse) ; Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE) | 80Prime MITI CNRS | ALADIN (IA-ESRE-0021, ESR / EquipEx+)
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Show more [+] Less [-]English. In bacteria, faithful DNA segregation of chromosomes and plasmids is mainly mediated by ParABS systems. These systems, consisting of a ParA ATPase, a DNA binding ParB CTPase, and centromere sites parS , orchestrate the separation of newly replicated DNA copies and their intracellular positioning. Accurate segregation relies on the assembly of a high‐molecular‐weight complex, comprising a few hundreds of ParB dimers nucleated from parS sites. This complex assembles in a multi‐step process and exhibits dynamic liquid‐droplet properties. Despite various proposed models, the complete mechanism for partition complex assembly remains elusive. This study investigates the impact of DNA supercoiling on ParB DNA binding profiles in vivo, using the ParABS system of the plasmid F. We found that variations in DNA supercoiling does not significantly affect any steps in the assembly of the partition complex. Furthermore, physical modeling, leveraging ChIP‐seq data from linear plasmids F, suggests that ParB sliding is restricted to approximately 2 Kbp from parS , highlighting the necessity for additional mechanisms beyond ParB sliding over DNA for concentrating ParB into condensates nucleated at parS . Finally, explicit simulations of a polymer coated with bound ParB suggest a dominant role for ParB‐ParB interactions in DNA compaction within ParB condensates.
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